A receiver/dryer is a common component of a refrigeration or air conditioning system, and receives excess refrigerant in the cooling cycle, separates vapor refrigerant from liquid refrigerant, and removes water and particulate matter.
One type of receiver/dryer includes a cylindrical canister with inlet and outlet fittings at one end which allow refrigerant to flow into and out of the canister. One of the fittings (typically the outlet fitting) is connected at its internal end to a pick-up tube, which extends downwardly through the canister to the lower end. Layers of filters and desiccant material surround the pick-up tube along its length. Refrigerant is directed into the inlet fitting and flows through the filter pads and desiccant material to the bottom of the canister. The filter pads and desiccant material remove particles and other impurities from the refrigerant. The refrigerant then flows upwardly through the pick-up tube to the outlet fitting.
One type of desiccant material for such a receiver/dryer is provided in a fabric bag which retains the desiccant and allows the desiccant to be easily located within the canister during assembly. Designs for such desiccant bags include a pouch, saddle-bag or donut-shape, and are shown for example in Searfoss, et al., U.S. Pat. No. 5,245,842; Kish, et al., U.S. Pat. No. 4,496,378; Wintersteen, et al., U.S. Pat. No. 5,179,780; Shiina, et al., U.S. Pat. No. 5,191,775; and Mosher, et al., U.S. Pat. No. 5,215,660.
A desiccant bag particularly lends itself to easy assembly within a receiver/dryer which has the lower end wall of the canister formed in one piece (or at least integrally) with the side walls of the canister. The lower end wall can be formed by drawing, impacting or spin-forming the sidewalls of the canister closed at one end. While all subsequent components must be inserted from the open upper end of the canister, such canisters have been found to be cost-effective to produce for certain applications.
In a receiver/dryer with an integral lower end wall, the desiccant bag, and any filters, baffles, etc., are introduced into the canister from the upper end. The pick-up tube is then pre-assembled with the upper end cap and inserted into the canister. The desiccant bag could also be initially located around the pick-up tube and introduced into the canister at the same time as the pick-up tube. The upper end cap is then fluidly sealed to the sidewalls of the canister by appropriate means, e.g., welding, brazing, soldering, etc., and the receiver/dryer is connected within the refrigeration system. By using such a desiccant bag, it is relatively easy to introduce the pick-up tube down through the canister as the desiccant remains contained within the bag and does not randomly disperse throughout the canister.
While the above receiver/dryers have received some acceptance in the marketplace, enclosing the desiccant in a bag adds labor and material cost to the receiver/dryer, and does not allow flexibility in using the bags in a wide variety of applications. For example, each bag is designed for a specific application and has a predetermined volume, porosity, material and desiccant composition, etc. To change the structure, material or composition of the desiccant bag for other applications, new bags typically must be manufactured. This can require tooling changes and ordering of new fabric and desiccant material, all of which can be time-consuming and expensive. Stocks of different sizes and types of desiccant bags also typically have to be kept on hand which can increase storage and inventory costs, and hence the over-all cost of the receiver/dryer.
As such, applicants believe that it would be desirable to use loose desiccant material for the receiver/dryer in certain applications. Such loose desiccant material can be less expensive to purchase and is easily adaptable to a wide variety of applications (i.e., does not have restrictions as to form or composition). The desiccant can just be added (poured) into the canister in the desired amount, with no additional labor or material costs.
In using loose desiccant material, however, it can be difficult to assemble the receiver/dryer when the canister is formed with an integral lower end. To begin with, the pick-up tube is typically pre-assembled with the upper end cap and secured thereto by, e.g., coining, crimping, or swaging, so as to ensure a fluid-tight connection. In so doing, the desiccant must be introduced into the canister before the pick-up tube is inserted, or else the end cap blocks the easy filling of the canister, as well as the introduction of subsequent components such as the upper baffle and filter pad. However, it can be difficult (or even impossible) to introduce the pick-up tube into the canister when the loose desiccant is randomly dispersed in the canister. Specifically, it is not desirable to force the pick-up tube through a loose bed of desiccant material. The desiccant can also flow through the pick-up tube opening in the lower baffle before the pick-up tube is inserted into the canister, and thus enter the lower, quiescent area of the receiver/dryer.
In addition, applicants believe that the pick-up tube has heretofore been formed essentially straight and vertical to allow the pick-up tube to be inserted through the various baffles and filter pads in the canister. In so doing, the upper end of the pick-up tube is necessarily connected to the upper end cap along the center-line of the canister. However, in some applications it can be desirable to mount a plurality of components to the top surface of the end cap. If the pick-up tube must be connected along the center-line, this can limit the ability to attach additional exterior components to the end cap, and hence limit the usefulness of the receiver/dryer for some applications. While it is known to form the outlet passage off-center on the end cap, cross holes must then be drilled transversely through the end cap to connect the outlet passage to the pick-up tube, which increases machining steps, labor costs, and wasted material.
As such, applicants believe there is a demand in the marketplace for a receiver/dryer which, although it includes an integral lower end, is simple to assemble and is particularly suited to accepting loose desiccant material to reduce the over-all cost of the receiver/dryer. Applicants also believe there is a demand for a receiver/dryer which allows for an off-center connection between the pick-up tube and the end cap such that there is flexibility in attaching exterior components to the end cap.